COLUMBUS, Ohio (AP) — The number of historic covered bridges in Ohio is dwindling, from what was once thousands to about 145 now, and preservationists say vandals and arsonists are chipping away at those still standing.

Ohio's number of original covered bridges is second only to Pennsylvania, which has more than 200, according to the Ohio Historic Bridge Association. The remaining wooden spans over streams and creeks sometimes are marred by graffiti, fire and other damage.

Association president David Simmons told The Columbus Dispatch (http://bit.ly/17HTjsz ) it's often tough to catch the vandals. Many of the bridges are in rural or isolated areas and don't carry traffic, and Simmons says that can attract firebugs.

An 1874 bridge with a rare, rounded shape was destroyed by arson in June in southeast Ohio's Vinton County.

"It was devastating to everyone," county engineer Ron Sharrett said. "The problem is that there is nothing you can do to reconstruct it. The entire bridge went down."

Sharrett said about $300,000 had been spent a decade ago to rehabilitate the bridge. The structure, known as the Ponn Humpback Bridge, was one of two of its kind in the country. The remaining one is in Virginia.

That case is under investigation as arson, as is an earlier fire at an 1881 bridge on Ohio University's Lancaster campus.

The January blaze in Lancaster caused an estimated $20,000 in damage to support posts and decking of the bridge. In that case, repairs were made and the bridge reopened to foot traffic.

It's one of 18 original covered bridges in Fairfield County, which has the most among Ohio's 88 counties. In northeastern Ohio, Ashtabula County also has 18, but some of them are newer.

Ohio's historic covered bridges were built from 1816 to 1919, Simmons said.

Some officials have tried to keep alive the tradition of such bridges by building modern versions.

Union County, for example, added three double-lane structures to its four remaining, single-lane originals, three of which are still used by traffic.